1. Field of the Invention
The present invention provides a structure for supporting a vibrator.
2. Related Art Statement
It has been studied to use a vibratory gyroscope as a turning angular rate sensor employed in a vehicle control system of an automobile based on a vehicle turning rate feedback system. Such a system detects the direction of a steering wheel itself by a turning angle of the steering wheel. Simultaneously, the turning rate of the vehicle is detected by the vibratory gyroscope, The system finds a difference by comparing the direction of the steering wheel with the actual vehicle turning velocity, and attains a stable vehicle control by correcting a wheel torque and a steering angle on the basis of this difference.
In a vehicle control system, a vibratory gyroscope and its vibrator is subjected to a wide temperature range including high and low temperatures. Such temperature range normally includes minus 40° C. to plus 85° C. and may be more wider in a more severe specification. Particularly, when a vibrator is made of a piezoelectric single crystal, the temperature dependency of the single crystal may affect the stability of the gyroscope. The assignee filed a Japanese patent publication 2001-12955A. In the publication, a vibrator is adhered to a supporting member with an adhesive having a tan δ of not higher than 0.1 within the temperature range for use, for preventing the deviation of Q value of a detection vibration with temperature change.
Further, Japanese patent publication 2003-28648A discloses a member for supporting a vibrator for use in a vibratory gyroscope. According to the disclosure, the supporting member is composed of an elongate rod bent in a complex form so that the vibrator is supported with the rod. It is also described that the supporting member is electrically connected with an electrode formed on the vibrator.
According to such supporting method, however, a substantial temperature drift may be observed, for example, in a high temperature region. For example, as shown in FIG. 7, even when the driving impedance is constant in low to room temperature range, the driving impedance may be rapidly increased in a range of 60 to 70° C. to result in temperature drift.